Hill and Cox have come up with new formulas that extend Einstein's understanding of the relationship between the relative velocity of two different bodies (A and B) in space, and the velocity they observe of a third body (C).

Relative velocity is the difference in velocity between A and B. When relative velocity is zero, both bodies see C moving at the same speed.

But as the relative velocity between A and B increases, they will record different readings of C's velocity.

When the relative velocity approaches the speed of light, formulas become undefined and special relativity breaks down.

Hill and Cox's formulas extend special relativity to a situation in which the relative velocity can be infinite. It can be used to describe what happens at speeds greater than the speed of light.

However, as with the original Einstein theory the formulas become undefined and break down when the relative velocity reduces to the speed of light.

"In both theories the speed of light remains a mathematical singularity," says Hill.

Uncharted territory

Hill says this mathematical fuzziness at the speed of light means we still don't know what will happen to basic matter when it actually passes through this velocity.

"You've still got this business that when you actually go through the speed of light you don't know what's going to go on," he says.

"Life is this place where we travel less than the speed of light and I have a feeling the world will change in some dramatic way as we move through the speed of light."

"All sorts of things could happen. Time and space could interchange."

He likens our current situation to that we were in before aircraft could fly through the sound barrier.

"People wondered what would happen - were we all going to disintegrate? Would the plane fall apart," says Hill. "It turns out passing through the speed of sound led to a big bang."

"I suspect going through the speed of light will be more interesting."